1. Field of the Invention
The present invention generally relates to a retarder, a liquid crystal display element, and a liquid crystal projector and, in particular, to a liquid crystal projector that has a compact body and that provides low light loss, high contrast, and high response speed by including a display element using an electric-field-controlled birefringence mode liquid crystal panel.
2. Description of the Related Art
Liquid crystal projectors are known that modulate light output from a light source using, for example, a transmissive liquid crystal display element so as to form light of an image and that project the light of an image onto, for example, a screen. Such liquid crystal projectors modulate light using liquid crystal display elements corresponding to R, G, and B primary colors and, subsequently, combines image light generated through the light modulation. Thus, the liquid crystal projectors can output a color image.
These known liquid crystal projectors employ a twisted nematic liquid crystal material as the liquid crystal display element. In recent years, a homeotropically-aligned electric-field-controlled birefringence mode liquid crystal display element has been used in order to increase the luminance, contrast, and resolution of the liquid crystal projectors. Additionally, in general, to increase the ease of manufacture, a transmissive liquid crystal display element is used for the liquid crystal projectors.
The homeotropically aligned liquid crystal display element can provide a significantly high contrast. However, when the homeotropically aligned liquid crystal display element is disposed in a liquid crystal projector, a strong electric field that is parallel to a substrate, known as a transverse electric field, occurs. This transverse electric field could disrupt the alignment directions of liquid crystal molecules, thus decreasing the light transmission efficiency.
To minimize the transverse electric field, a method has been proposed in which the polarity of the potential of an electrode is reversed between screen displays, known as a field reversing drive method. However, to perform this field reversing drive method, a large pixel potential capacitance is required for maintain the pixel potential for one field period. Accordingly, the aperture ratio of the pixel decreases, thus decreasing the light transmission efficiency.
Additionally, the above-described decrease in the light transmission efficiency of the liquid crystal display element makes the production of a high-resolution liquid crystal projector using this liquid crystal display element difficult.
In addition, a method for increasing the light transmission efficiency and the response speed of a liquid crystal display element has been proposed in which the non-uniform alignment directions of homeotropically aligned liquid crystal molecules due to the transverse electric field are controlled by controlling the pre-tilt angles of these liquid crystal molecules. However, in this method, a high contrast ratio, which is an advantage of the homeotropically aligned liquid crystal element, cannot be achieved, and therefore, the production of a transmissive liquid crystal projector using the homeotropically aligned liquid crystal element is difficult.
Accordingly, a structure is proposed in which a retardation unit composed of an optical anisotropic element is disposed between a liquid crystal element and a polarizer disposed on both sides of the liquid crystal element. In this case, the optical anisotropic element disposed between a first polarizer and the liquid crystal element or disposed between a second polarizer and the liquid crystal element is tilted at an angle in accordance with the alignment directions of liquid crystal molecules of the liquid crystal element. In such a structure, the light transmission efficiency can be improved while maintaining the high contrast ratio. In addition, the response speed can be increased (refer to, for example, Japanese Patent Application No. 2004-191938).